Avril Lavigne is ready to hit the mall. As her tour bus pulls into the parking lot of the Somerset Collection, a shopping center in Troy, Mich., the singer yanks up her sagging tube socks and slips on a pair of retro Vans sneakers. She drags a comb through her long hair, spot-checks her makeup and heads in. The 19-year-old Lavigne would love to drop into Rampage and try on baby T's or maybe pick up a pair of Converse Chucks at Foot Locker, but she's actually here to play songs off her forthcoming album, "Under My Skin," and it's hard to shop with hundreds of screaming fans in tow. There are girls everywhere. They're packed around the impromptu stage, waving homemade AVRIL WE LUV U banners from the tiers above, shooting cell-phone photos from the escalator. They sport looks from videos off Lavigne's multiplatinum debut, "Let Go"--the sideways baseball cap of "Sk8er Boi," the tank top and tie from "Complicated." An army of Avrils has invaded the upscale suburban mall, and nothing--not even a Steve Madden shoe sale--can tear them away from their tomboy hero.

Lavigne has not forgotten where she came from. That's why she agreed to do a free promotional mall tour two months before her album's May 25 release. The scrappy Canadian kid quite literally got her start performing in Ontario shopping complexes before becoming, at 17, one of America's top-selling artists. Often referred to as the anti-Britney, she sang about kicking butt rather than baring it on her 2002 debut, and inspired legions of girls to leave the house dressed in their brothers' T shirts and ties. "I read that I was supposedly mad at my fans for dressing like me," Lavigne said earlier in her tour bus. "They quoted Hilary Duff saying, 'Avril needs to appreciate her fans more and blah, blah, blah.' I'm like, excuse me? First off, it's not even true. I never said that. And second, who the hell cares what she has to say about my fans? Whatever. Hilary Duff's such a goody-goody, such a mommy's girl." When asked if she's ever met Duff, she slinks down on the couch and mumbles "no." Then, in a mocking, sugarcoated voice, she says, "But I'm sure she's really nice and really sweet. I'm sure she's all smiles."

Believe it or not, Avril Lavigne has matured. The high-school dropout has gone from cute to classically pretty. She's even started wearing skirts every once in a while, but not "the a---showing kind that everyone else wears." Part of her journey into adulthood includes writing the words and melodies for "Under My Skin" rather than handing over her raw ideas to hitmakers The Matrix, the songwriting team largely responsible for her last CD. Her new songs are rougher and darker than the bright, addictive pop of "Let Go," while her voice, which is quite emotive and believable now, has lost some of its girly high pitch. "It's a more serious album in ways," says Lavigne, curled up on her couch. The petite singer pulls her hands into the sleeves of her oversize, camouflage green sweat jacket and, for the first time during the interview, has trouble making eye contact. "I wrote a song about my grandpa called 'Slipped Away.' He died when I was on tour. It's the first death I ever experienced. I never had problems singing a song before, but every time I tried, it just wasn't right. My voice wouldn't have enough emotion in it. One night I finally did it in one take. I was shaking inside. As soon as I was done, I stepped away from the mike and started bawling."

Just as there is a sentimental soul under Lavigne's sassy, gum-smacking exterior, there's also an endearing naivete that would likely make Lavigne roll her eyes if she were ever able to meet herself. A prominently displayed collage with the words FRIENDS FOREVER sits on a shelf next to her tour-bus bed. It was made by her best friend, Monique. "Here we are in our pajamas on the Sunset Strip," she says with a giggle as she points to one picture. "And here we're bowling, then roasting marshmallows at this cool restaurant..." In ways, she's still a lot like the fans who come to see her. At her mall appearance, girls in their midteens hold up Avril collages cut from magazine photos as they sing every word to the old hits, mouth a few to her new single "Don't Tell Me" (out this week) and sway to the songs they're hearing for the first time. Some of the younger kids giggle when they hear a curse word in the bitter breakup number "Everything I Wanted," while the older ones cheer to lines from her single: "Don't think that your charm and the fact that your arm/Is now around my neck will get you in my pants/ I'll have to kick your a--/Get out of my head/Get off of my bed/ Yeah, that's what I said."

After the show, she worries about how her new album will be received by her tween-age fans. "I don't know if some of this stuff is gonna be too mature for them," she says. "When I play those new songs in front of the kids, they have no idea what the hell I'm talking about. Now I'm like, Oh f---. I hope I don't scare people away."

Lavigne is older than most of the girls who swarm into the mall to see her. If she were their neighbor, the singer would likely be hanging out with their older siblings and watching cool videos on Fuse rather than herself on MTV. Her new album is an attempt to balance out her old-kid sensibilities with her newer adult tastes, and it's likely to grab listeners who are in the same tumultuous stage of life. And if they don't like it? "I beat up a boy one time," she says, munching on a carrot. It seems she was in a record store when the kid yelled out a pretty disgusting obscenity about her. "I was like, 'I'll just ignore him,' and I left. He followed me. I kick him in the nuts, throw him on the sidewalk. I guess he thought I wouldn't react 'cause I'm just that girl on TV. Funny thing is that while I had ahold of the guy's shirt, someone's like, 'Oh my God! It's Avril Lavigne!' and they shake my hand while I'm in the middle of beating someone up."

So she's famous and she can fight. The only thing left for Lavigne to prove is that she can stand on her own. The singer, who got her start singing church hymns and country tunes at county fairs, only just moved out of her parents' Napanee house and into her own Toronto apartment. She says she also dodged all record-company supervision when it came to writing her second album. She flew to L.A. to work with singer-songwriter Chantal Kreviazuk and ended up hanging with new buddies like guitarist Ben Moody of Evanescence fame (he co-wrote a song on her album). She also took the opportunity to sneak into Sunset Strip bars and frequent trendy tattoo parlors: "See, it's a star," she says, proudly displaying the new art on her inner wrist. Lavigne did not let her record company, Arista, hear any music until she had written and recorded it her way. "There was no way I was gonna write songs and send them to people to rewrite them like I did last time," she says. "I need to feel I'm doing this on my own."

There are plenty of people around to tell Lavigne what to do, but that doesn't mean she'll listen. Her tour manager advises her not to spend too much time signing autographs for kids outside the mall, but she spends at least 20 minutes scribbling her name on CDs, tennis shoes and backpacks. She even takes a photo with three love-struck skater boys. These are the fans whom Avril will lose when she grows up. But for now, she's one of them--and happy to hang outside the mall.